The present invention relates to a method of producing an interiorly sterile packaging container from a blank of thermoplastic material which is heated to moulding temperature and, with the aid of a pressure difference, is urged into abutment against an adjacent moulding surface. The present invention also relates to an apparatus for producing an interiorly sterile packaging container from a blank of thermoplastic material, the apparatus comprising a number of processing stations arranged in sequence.
A generally distributed type of packaging container for various types of drinks, for example water and soft drinks, is the blow moulded plastic bottle which consists of thermoplastic material and is normally produced from a blank, a so-called preform, or an extruded parison. A packaging container of this type may be manufactured rationally and at high speed. Moreover, the production method affords good hygiene, since the blow moulding operation requires such an elevated material temperature that the preform, in connection with the blowing operation, becomes more or less sterile. In order to maintain the interior freedom from bacteria also after the blowing operation and during the subsequent handling of the finished packaging container, it is however, necessary that the container be closed in bacteria-tight fashion immediately after manufacture. This may either take place temporarily as a preparation for later filling and sealing of the packaging container, or after a filling of the container with the desired contents undertaken immediately after the blow moulding operation.
In those cases when it is desirable to provide a guaranteed sterile package, for example for packaging previously sterilized contents to maintain long shelf life, a supplementary sterilization of the interior of the packaging container is however required, which may be put into effect with the aid of one of the known and accepted efficient methods which are employed for other types of packaging containers, for example sterilization using chemical agents (hydrogen peroxide) and/or thermal or radiation sterilization.
It is thus previously known in the art to sterilize different types of ready-made packages by means of, for example, chemical sterilization. The ready-formed packaging container is, in such instance, treated interiorly with the chemical sterilization agent in liquid, vapour or gas form. After having ensured that the whole of the interior of the packaging container comes into contact with the sterilization agent, the agent is once again evacuated with the aid of, for example, sterile hot air, in which operation both the air current and the elevated temperature ensure that residual quantities of sterilization agent in the finished packaging container will be at a minimum. However, sterilization of the finished package suffers from certain drawbacks since, on the one hand, a considerable quantity of sterilization agent is consumed because of the relatively large volume of the packaging container and, on the other hand, in certain types of packaging a containers it may be difficult to ensure that pockets such as inner corners and the like are sterilized adequately. The removal of the sterilization agent is correspondingly impeded by the volume and configuration of the packaging container and furthermore unavoidably entails a heating of the packaging container which, in for example blow moulded plastic bottles, may result in their thin-walled sections becoming weakened or deformed. Finally, the process is time-consuming and difficult to integrate rationally in the production and filling process.
There is thus a need in the art to realise a method which makes for the production of an interiorly sterile packaging container from a blank regardless of the configuration of the finished packaging container and without the risk of damage to such containers.
One object of the present invention is therefore to realise a method of producing an interiorly sterile packaging container manufactured by blow moulding of a blank of thermoplastic material, the method making it possible, for example with known types of chemical sterilization agents, to integrally realise a sterilizing treatment during the production of a filled and sealed, ready-moulded packaging container.
A further object of the present invention is to realise a method of producing an interiorly sterile, blow-moulded packaging container, the method avoiding separate handling of the sterilized preform/packaging container before this is filled with the desired contents and finally sealed in a satisfactory manner from the hygienic and sterile points of view.
Yet a further object of the present invention is finally to realise a method of producing an interiorly sterile packaging container, the method not only ensuring optimum sterilization conditions, but also obviating the need for separate handling of the sterilized blank/packaging container between the actual instant of sterilization and the filling/sealing operations and thereby eliminating the majority of the above-outlined drawbacks from which prior art methods suffer.
The above and other objects have been attained according to the present invention in that a method of the type described by way of introduction has been given the characterizing features that the blank is first heated to a temperature above the dew point of a gaseous sterilization agent which is thereafter brought into contact with the interior of the blank for a certain period of time, and that the blank is brought to an elevated temperature suitable for a moulding caused by the above-mentioned pressure difference.
Preferred embodiments of the method according to the present invention have further been given the characterizing features as set forth in appended subclaims 2 to 10.
By causing sterilization, using the method according to the present invention, to take place before reforming of the blank into finished packaging containers, it will be possible, because of the smaller volume of the blank and thereby the reduced interior surface area, to reduce the necessary quantity of sterilization agent and moreover independently of the configuration of the finished packaging container. The blank or the preform is normally of cylindrical configuration with rounded, closed end, and this form is well-suited for efficient and rapid sterilization. Moreover, sterilization of the blank instead of the finished packaging container entails a reduced quantity of sterilization agent per packaging container, which is also an advantage in view of any possible residual quantities in the finished, expanded packaging container. Nor is the preform sensitive to heating, instead the heating operation is rather an advantage since it gives additional heat which-facilitates the later heating to moulding temperature, with the result that the overall time for the process may be kept shorter than if sterilization had taken place separately after the moulding or forming operation.
There is further a need in the art to realise an apparatus for producing a sterile packaging container, the apparatus including means for making possible the rapid and reliable sterilization integrated with the production cycle proper. It is desirable that the apparatus be designed such that the risk of reinfection is minimal, at the same time as its design and construction are simple and make for a rapid and reliable production of blow-moulded, sterile, filled and sealed packaging containers.
One object of the present invention is therefore to realise an apparatus for producing an interiorly sterile packaging container from a blank of thermoplastic material, the apparatus, in addition to the customary stations for forming, filling and sealing of packaging containers, also including means for a sterilization process integrated in the production cycle proper.
A further object of the present invention is to realise an apparatus which, despite its substantially conventional design and construction, includes means for sterile treatment of the packaging container blanks.
Yet a further object of the present invention is to realise an apparatus of the above-outlined type, the apparatus making for a continuous, protected handling of the packaging container blanks throughout the entire production cycle of filled and sealed sterile packaging containers.
Still a further object of the present invention is finally to realise an apparatus of the above-outlined type, the apparatus as a result of its design and construction obviating the need for separate handling of sterile packaging containers and/or blanks, so that the risk inherent in prior art apparatuses of reinfection is eliminated.
The above and other objects have been attained according to the present invention in that an apparatus of the type described by way of introduction has been given the characterizing feature that it includes at least two stations for heating of the blank, and an interjacent station for sterilizing treatment of the blank.
Preferred embodiments of the apparatus according to the present invention have further been given the characterizing features as set forth in appended subclaims 12 to 20.
By realising, according to the present invention, an apparatus for producing interiorly sterile packaging containers by blow moulding, the apparatus not only including previously known types of sequentially arranged processing stations but also a station intended for sterilization of the blank placed interjacent two heating stations, it becomes possible to realise a compact and efficiently operating machine which ensures that the total production of filled and sealed, sterile packaging containers takes place without the packaging containers or blanks departing from the apparatus for the purpose of their production, which ensures an optimum result. The placing of the sterilization station between a first heating station for heating the blank to sterilization temperature and a second heating station for heating the blank to moulding or forming temperature reduces the overall size of the machine and increases its efficiency.